First off, Microsoft added a few new general options that app developers will surely appreciate. For the previously announced unified developer registration (across the various Windows device platforms) it announced it will now accept a credit card alternative -- specifically eBay, Inc.'s (EBAY) PayPal. It also now allows developers to reserve names of their upcoming apps up to 12 months in advance.

Second, it offered consolidated app options that make it easier for developers to deploy to multiple platforms and for consumers to partake in those various offerings. Also included are a set of universal pricing tiers, which will allow customers to pay once and download a participating developer's app on all Windows platform. Developers also have the option (and are encouraged) to make in-app content universal (so purchase on one platform and you'll get it on you installations on all your devices).

Tired of getting stuck with low-res. downloads for apps you've already purchaed? Microsoft's new Universal Apps let developers offer a single purchase that gives customers access to the highest definition app package on any compatible platform.

Looking ahead, this could provide Microsoft with a key competitive advantage over Google Inc. (GOOG) and Apple, Inc. (AAPL), which typically force you to rebuy apps on each new kind of device if you want the latest and greatest experience (iOS developers allows you to download previously purchased iPhone apps on iPad, but iPad-specific versions of apps require repurchasing).

Even though Windows Phone's market share is virtually nonexistent, if customers can buy a Windows Phone and get access to most/all their favorite Windows 8.x apps for free, it seems many will be much more likely to take the plunge.

Developers have the ability to set one set of permissions and the app certification policies have been made homogenous across the various tiers. To support a specific kind of device developers need only upload a "package" which will be available to download on compatible devices via the Windows/Windows Phone Stores.

The store will automatically select the appropriate package.

Windows Phone developers may wish to use the older Silverlight technology ("xap" packages, or *.xap files), which Microsoft is still clinging to, but with the latest and greatest Windows Phone 8.1, they now have the option to move to "AppX" (*.appx) style packages. With AppX packages, developers can write a single app that is auto-customized for various platforms by Microsoft's APIs. Obviously some developers will want to put in the extra work to specify explicitly optimal user interfaces for their app for each applicable screen size and input kind. But for small businesses and casual app developers this is a potential game-changer.

Microsoft is now offering helpful reminders at submission time to prevent developers from forgetting to submit a privacy policy, a common (and frustrating) cause of rejection for first-time Windows/Windows Phone developers in the past.

Finally, Microsoft has redesigned its Dev Center for Windows and Windows Phone to offer better guides to creating apps for developers of a variety of skill levels. And it has promised to cut down on submission times.

We'll have to see how well all of these things work out in practice, but as with the recent Windows 8.1 Update 1 (which added improved mouse and keyboard support), Microsoft definitely appears headed in the right direction. In the long term it plans to integrate Xbox apps into its Universal Apps platform. With the large Windows and Xbox market shares, it may be able to drive growth synergistically in the tablet and smartphone space.

I believe what they're referring to us the fact that you can purchase the app across platforms as well. The scenario you mention is still the same OS (Android) on both tablet and phone, so of course your android app will work on both. The goal of universal apps is to write once and have it on everything - phone, tablet, desktop, laptop, and future devices as well. It would be akin to your Android apps running natively on Chrome OS or iOS apps running on OSX.